This invention relates to a battery charging apparatus, a power supply, and an attachment allowing the charging of both constant voltage rechargeable batteries and constant current rechargeable batteries, and allowing different shaped rechargeable batteries to be accomodated.
There are different types of rechargeable batteries that can be used repeatedly after charging. Alkali rechargeable batteries such as nickel-cadmium and nickel-hydrogen batteries are already in widespread use. Nonaqueous rechargeable batteries such as lithium ion batteries, which are small and have a high capacity, have recently gained attention.
Alkali rechargeable batteries have the property that the battery voltage increases during charging and then decreases when a full charge is reached. Therefore, alkali rechargeable batteries are normally charged with a constant current using a battery charger having a constant current output terminals.
On the other hand, nonaqueous rechargeable batteries such as lithium ion batteries behave in a manner that does not allow constant current charging. Since nonaqueous battery voltage continues to increase with constant current charging even after reaching a full charge, full charge cannot be detected by sensing the battery voltage and over-charging results. Consequently, nonaqueous :rechargeable batteries are charged with a constant voltage as described by Japanese Patent Disclosure Hei 4-183232 (1992).
Since alkali rechargeable batteries and nonaqueous rechargeable batteries have different charging methods, it is necessary to charge them with a constant current and constant voltage respectively.
Further, a battery pack housing nonaqueous rechargeable batteries is smaller than that housing alkali rechargeable batteries. This is because nonaqueous rechargeable batteries are smaller and have a higher power capacity as compared to alkali rechargeable batteries. Consequently, a nonaqueous rechargeable battery pack has a different shape than an alkali rechargeable battery pack and cannot be attached as is to electrical equipment designed for alkali rechargeable battery pack specifications.
It is thus the primary object of the present invention to provide a single battery charging apparatus that can charge both alkali and nonaqueous rechargeable batteries using charging terminals to output a constant current and adapter terminals to output a constant voltage.
It is yet another object of the present invention to provide an apparatus that makes it possible to attach rechargeable batteries of different shapes to electrical equipment.